mtx calls for 2 4 inch ports like 14 inch's long for the 6000's series, 15, used the calculator at the12volt, and it said one 4 inch 6.2 inches long for the same frequency, now ive always used this caculator for my ports and it always worked fine,, but i wondering why mtx would use 2 ports insetad of one?

 

makes sence

 

Yep - one 4" is no where near enuf for a 15" driver. One of the freebie calc pages has a minimum vent area calculator..

 

all the same i used a sngle 4 on a mmats pro cast 15 in a abc box and it sounded great

 

try this clicky

 

mani dont like the idea of using 2 ports that that would be 12 in total for the abc box, ouch

 

^ In an ABC you are cheating the area a bit because the low tuning uses both vents. There is less excursion at the upper tuning so chuffing is reduced over a regular ported box.

Double vents in an ABC makes for 6 vents, not 12.. Plus you could try moving up to a 6" vent - it has just over double the vent area of a 4"

 

if i use 2 ports per sub like mtx calls for it would be 12

 

how big are you trying to make the box and at what tuneing? you could always go with areoports to

 

3 cubes per sub, and 3 for the second chamber,
tuned to 35z